1. Field of the Invention
This invention relates to wheel alignment rim clamps, i.e., clamps for affixing wheel alignment measuring devices to the wheels of vehicles. More particularly, it concerns an improved design for claws or fingers present in these rim clamps to grip the wheel.
2. Description of Prior Art
Wheel alignment systems have been in common use for generations. In such systems, it is necessary to make a physical connection between the wheels being aligned and various gauges and measuring devices. In some systems, this can be carried out by attaching the gauges or measuring devices to the spindle or axle which carries the wheel, but by far the more common approach is to mount the gauges or measuring devices to the wheel itself.
The mounting of the alignment equipment on the wheel is usually carried out by first affixing an adjustable gripping device to the wheel and then mounting the measuring device on an appropriate fitting on the gripping device. These gripping devices are known in the trade as "rim clamps" or "wheel clamps" since they are mechanical devices which physically "clamp" onto the wheel. It is conventional for the rim clamps to have a plurality (usually three or four) of fingers or claws that gain a purchase on the rim of the wheel to carry out the actual attachment.
Conventional rim clamps were designed for use with pressed steel wheels and high aspect ratio tires. With these prior wheel-tire combinations it is easy to locate surfaces to which the gripping devices can attach. There generally is a good gripping surface provided by the substantial clearance between the sidewall of the tire and the outside lip of the wheel rim. Similarly, conventional steel wheels often have painted horizontal surfaces on their faces which can serve as engagement points. Also, steel wheels generally carry decorative wheel covers that cover any scratches which the gripping devices might cause. Because of these advantageous features of old style wheels and tires, conventional gripping devices have taken the form of serrated rods, "fat" hooks and rubber "friction" pads. Typical examples of these devices are shown in FIGS. Prior Art A, B, and C.
With the wide adoption of "mag" wheels and modern low aspect ratio tires, a range of failings of the prior rim gripping devices have surfaced. In particular, the cast mag type wheels do not present the convenient purchase points present in their predecessors. The clearance between the tire sidewall and the lip of the wheel rim is often too small. Often the rim lip is much thicker than with steel wheels. Also, the high cost of mag wheels has made their owners much more particular about the wheels' appearance and unwilling to accept the introduction of scratches, mars and the like during the mounting of alignment instruments. Moreover, the visible surfaces of the wheels are often highly polished so as to prevent easy use of the "friction" type attachment pads. Some of these problems are illustrated in FIGS. Prior Art D and E.
These problems have led to poorer quality mounting of alignment instruments to wheels than was previously the norm, with resulting slippage during alignment and in some cases unexpected accidental decoupling of the alignment instruments from the wheels.
It is a fundamental object of this invention to provide a rim clamp claw which does not present the failings of these prior devices.
It is also an object of this invention to provide an improved rim clamp incorporating this new claw which can accommodate the broad variety of rim shapes and materials and tire geometries now in use, preferably gripping the outside surface rim but also, if desired being adaptable to grip an inside surface.
It is another object of this invention to provide a claw or finger for use with a rim clamp which achieves a good purchase on a wide range of wheels without visibly scratching or marring the wheel rim.
It is a further object of the invention to provide fingers or claws for a rim clamp which are adapted to clamp a wheel by grasping a portion of the rim which is normally covered by the tire.